The invention relates to releasable torque transmitting couplings and it is concerned more particularly with a self-releasing clutch which will disengage when a predetermined amount of torque is experienced.
While the principal purpose of torque limiting clutches is to protect various types of power driven equipment against overload, such clutches have heretofore also been perfected to take care of several specific requirements. For instance, in many installations it is desirable that once the clutch has become disengaged due to an overload it should stay disengaged as long as the overload condition persists, and that the clutch can be reengaged by torque reversal at will when the overload condition has abated to the point where operation of the driven equipment can be resumed. When the clutch idles, that is, while its driving member continues to rotate and its driven member is at a standstill, friction losses between the driving and driven members and wear of the relatively engageable and disengageable clutch elements should be kept to a minimum.
Further, the torque load at which the clutch becomes disengaged should be precisely fixed, that is, disengagement should take place at the exact moment when the torque reaches a given limit. In its engaged driving condition the clutch should provide a positive driving connection between the driving and driven shafts, that is, there should be no gradual yielding between the driving and driven clutch parts. The driving connection should be disrupted instantaneously when the given torque limit has been reached. In some installations it is also desirable that the driving and driven clutch parts can be reengaged in only one rotatively adjusted position relative to each other. This requirement usually has the purpose of maintaining a time relationship between several operating units that are driven from a single power source. Provisions should also be made to vary the torque limit at which the clutch will automatically disengage under an overload, and such variation to increase or decrease the torque limit should be possible conveniently without dismantling the clutch. Another provision which is frequently desired is that the clutch should be unidirectional, that is, it should provide torque control in one direction and solid drive in the opposite direction. Incorporated herein by reference is U.S. Pat. No. 3,893,553.
Additionally, fluid or other contaminates entering a mechanism like the present invention may cause premature wear or failure. For example, fluid or other contaminants may enter during a parts cleaning procedure. Therefore, where exposure to fluid or dirt is possible, a clutch capable of limiting the exposure of internal parts to fluids or contaminates would be desirable.
Furthermore, clutch characteristics may change upon clutch break-in. Therefore, a clutch that is manufactured to take into account break-in patterns would be desirable.